Alkali hydroxides for use in single-powder photographic developers



United States atent ALKALI HY DROXIDES FOR USE IN SINGLE- POWDER PHOTOGRAPHIC DEVELOPERS Ralph W. Baxendale, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application November 26, 1954 Serial No. 471,510

4 Claims. (CI. 96-66) This invention relates to photographic developer compositions, the components of which are mutually compatible and can, therefore, be packaged for merchandising as a mixture in a hermetically sealed package. Such photographic developer mixtures are commonly termed single powder photographic developers, and the present invention more particularly relates to single powder developers containing alkali hydroxides which have been treated to lessen or to prevent their reactivity with components of the atmosphere as well as with other components of single-powder developers. This invention also relates to methods of treating alkali hydroxides with one or more protectant compounds to lessen or to prevent interaction with the atmosphere, or with organic developing agents, and to the treated alkali products produced thereby.

For many years photographic developer powders have been packaged with the developing agents separated from the alkaline components to prevent interaction. More recently it has been found that some developer mixtures may be protected by the addition of certain protectants so that the developing agents may be mixed directly with the other components of the developer and the resulting developer mixture can be packaged as asingle powder developer.

Such single powder developers may contain, for example, an organic developing agent such as monomethyl p-aminophenol sulfate, hydroquinone, p-aminophenol hydrochloride, p-aminophenol sulfate, pyrogallol, p-hydroxyphenyl glycine, catechol, diaminophenol hydrochloride, 1-phenyl 4-methyl-3-pyrazolidone, 1 phenyl 4,4-dimethyl-3-pyrazolidone and suitable mixtures thereof, stable alkaline buffer salts such as sodium carbonate monohydrate, sodium metaborate tetrahydrate (Na B O .4H O) and sodium tetraborate pentahydrate (Na B O .5H O); and protectants such as boric anhydride, metaboric acid, phthalic anhydride and sodium or potassium bisulfites and metabisulfites and may also con tain the other well known ingredients normally present in a developer such as sodium sulfite and potassium bromide, the normal and known function of the alkali sulfite being that of preservative, lessening the oxidation in solution of the organic developing agent, while the known function of potassium bromide is that of a restrainer particularly inhibiting fog formation in the development of the silver image.

However, when employing sodium hydroxide in such protected single powder mixtures, the strongly hygroscopic nature of sodium hydroxide and the dampness of its surface has frequently been found to be the cause of discoloration even in the presence of the above named protectants. This is particularly serious since it is often desirable to add a strong alkali such as sodium hydroxide to a developer powder to give higher total alkalinity, or to single powder mixtures to overcome the acidity introduced by the protectants.

An object, therefore, of the present invention is to provide single powder developers containing an alkali hydroxide which has been treated so as not to react with atmospheric moisture or with the other components of the single powder developer.

Another object of this invention is to provide single powder developers containing sodium, potassium, or lithium hydroxide from which developing solutions which are colorless, fully balanced and of a proper -degree of activity can be prepared.

Another object of this invention is to provide a method of treating alkali hydroxide to reduce its hygroscopic properties.

Yet another object is to'provide a method of coating particles of alkali hydroxides with a coating which does not react with the atmosphere or with other single powder developer components.

Another object is to provide particles of alkali hydroxides having a coating thereon which does not react with the atmosphere or with single powder developer components. Other objects will appear hereinafter.

In accordance with the present invention these and other objects may be attained by first treating the alkali hydroxide with an ester of an organic acid or an ester of an inorganic acid. Alkaline hydrolysis will occur in which the alkali salt of the acid and an alcohol will be formed. The alcohol is then expelled leaving the alkali hydroxide covered with an adherent alkali salt coating of the selected acid.

The preferred treatment involves employing an alkali hydroxide in particle form and an ester which is a liquid at room temperatures, and which will generate an easily volatile alcohol. Generally, weighed amounts of the reactants are employed. An amount of the ester equal to 1% to 15% by Weight of the amount of alkali to be treated is mixed thoroughly with the alkali until the reaction has gone to completion. The alcohol formed is suitably expelled, for example it is allowed to evaporate, is driven off by heating, or is removed under reduced pressure.

Once the reaction has beencompleted and the alcohol and/ or solvent driven off, a product comprising an alkali hydroxide core having an adherent alkali salt coating thereon is obtained. When this coated product is exposed to atmospheric conditions, it is found that the rate of moisture pick-up is very much slower than is the case with untreated alkali hydroxide. Such coated alkalis can be easily handled under the usual atmospheric conditions, whereas untreated alkalis become very damp after short exposure and eventually dissolve in the water which they absorb. The treated compounds can be packed in the soda portion of photographic developers without causing caking. When added to single powder photographic developer mixtures the treated compounds retard deterioration of the mixture and do not cause caking of the mixture.

This invention is further illustrated in the following examples:

Example 1 these pellets were placed in an open 50 cc. beaker and exposed to the atmosphere for 5 hours they remained dry and free-flowing. Untreated pellets exposed under the same conditions picked up moisture and caked badly after 20 minutes.

Example 2 Lithium hydroxide monohydrate was given a protective coating by the following treatment: 50 grams of lithium hydroxide monohydrate was mixed with 1.2 cc. of ethyl acetate and the mixture was warmed on a steam bath for several hours until the odor of the ester had disappeared. .The alcohol formed in the reaction was removed by evacuating the reaction flask for five minutes. The product Was white and free-flowing and comprised lithium hydroxide coated with lithium acetate. It showed no tendency to cake when exposed to air.

Example 3 The storage properties of finely powdered sodium hydroxide were improved by the following treatment: 50 grams of finely powdered sodium hydroxide was mixed with 1 cc. of diethyl phthalate and the mixture was thoroughly blended. Allowing the mixture to stand at 50 C. for 16 hours resulted in a dry, white, very freeflowing product and comprises sodium hydroxide coated with sodium phthalate. This product showed no tendency to cake when stored in a screw cap bottle, while untreated sodium hydroxide caked considerably when stored under the same conditions.

Example 4 Granular sodium hydroxide was given a protective coating in the following manner: 50 grams of granular sodium hydroxide was mixed with a solution of 5.2 cc.

of ethyl benzoate in 20 cc. of ligroim. This mixture was allowed to react at room temperature for 16 hours. The solvent was then drained and the product dried by warming under reduced pressure. The granules were covered with a pale brown coat of sodium benzoate. When grams of this product placed in a 50 cc. beaker was allowed to stand at room atmosphere conditions there was little tendency for water pick-up and caking. Untreated granular sodium hydroxide exposed under the same conditions picked up a considerable amount of water and caked badly within 30 minutes.

Example 5 To illustrate the operation of the invention with esters of inorganic acids the following procedure was used. Fifty grams of granular sodium hydroxide was mixed with a solution of 1.4 cc. of ethyl orthosilicate in 20 cc. of ligroin. The mixture was allowed to stand at room temperature for 16 hours after which the solvent was drained oil. The product was washed with ligroin and dried, yielding pale yellow granules. These granules showed less tendency to pick up moisture and cake than the untreated sodium hydroxide.

Example 6 This example demonstrates the use of a method of accelerating the ester hydrolysis reaction between an alkali hydroxide and an organic acid ester.

One hundred grams of granular sodium hydroxide was mixed with 3.3 cc. of diethyl oxalate and mixed thoroughly. When the reaction had started the mixture was placed in a covered Buchner funnel and a warm stream of air forced up through the mixture at a slow rate. The reaction proceeded to completion in about one hour, giving a dry white product. On the other hand, using the same proportion of reactants, the mixture formed a yellow-colored product "after standing for 24 hours at room temperature. This product became more deeply colored on further standing. The differences in quality of the products was quite evident when they were packed in a single-powder photographic developer formula of the following type.

Grams Elon 2.5 Hydroquinone 5.0 Sodium sulfite- 25.0 Sodium borate.5H O 25.6 Diethyl oxalate treated sodium hydroxide 7.1 Potassium bromide 1.8 'Boric anhydr 0.7

This powder did not discolor or otherwise deteriorate when stored at 120 F. However, the already discolored product packed in the same formula and stored under the same conditions gave a single powder of less attractive appearance.

Example 7 To illustrate the use of the treated sodium hydroxide in photographic developer powder packing the following powder was prepared:

Grams Sodium sulfite, desiccated 22.5 Sodium tetraborate pentahydrate 25.8 Potassium bromide 1.8 Ethyl benzoate treated sodium hydroxide 3.1

This mixture, which represents the salt portion of a photographic developer powder remained free flowing after storage of 6 weeks at 50 C. A similar powder in which untreated sodium hydroxide was used caked severely when stored under the same conditions.

Example 8 This example illustrates theuse of ester treated lithium hydroxide as an addend to single powder photographic developer mixes. The following developer powder was prepared:

I Grams Elon (p-methylaminophenol sulfate) 2.5 Hydroquinone 5.0 Sodium sulfite (desiccated) 22.5 Sodium tetraborate pentahydrate 26.3 Potassium bromide 1.8 Phthalic anhydride 1.2 Ethyl benzoate treated lithium hydroxide 0.7

When incubated at 50 0., this developer powder had no tendency to discolor or deteriorate. A similar formula using untreated lithium hydroxide was unusable after the same incubation treatment.

When incubated at 50 C. this developer powder was substantially unchanged. -A similar formula using untreated sodium hydroxide'discolored and deteriorated.

Example 10 To give sodium hydroxide a protective coating the following method was used: 50 grams of granular sodium hydroxide was thoroughly mixed with 1 cc. of diethyl phthalate and the mixture allowed to stand 24 hours at 50 C. This resulted in a product that was dry and freeflowing. 5 grams of the treated sodium hydroxide was placed in an uncovered 50 cc. beaker and exposed to room atmosphere conditions for 8 hours after which the product was still uncaked and free-flowing. A sample of untreated sodium hydroxide exposed under the same conditions became very damp andseverely caked.

Example 11 1f the preparation described in Example 10 above is packed in a single-powder developer formation of the type given below, the single powders occasionally show some tendency to discolor when stored at elevated temperatures such as may be encountered in tropical regions. For such high temperature conditions -it is desirable to recoat the alkali hydroxide particles with a second protective laYQL. Accordingly, powdered chlorophthalic anhydride was mixed with the caustic, which has been treated as in Example '10, in a concentration of 1 percent by weight. After thorough blending, the mixture was allowed to stand in a closed container for 24 hours at 120 F. whereby a second integral coating of sodium chlorophtha'late was formed over the first coating. The resulting product packed in the following single-powder developer formula:

. Grams Elon 5.0 Hydroquinone 10.0 Sodium sulfite 72.0 Sodium .borate.5H O 25.6

Diethyl phthalate treated sodium hydroxide which has been treated with chlorophthalic anhydride" 13.5 Potassium bromide 5.0 Boric anhydride 1.3

The formula did not discolor or otherwise deteriorate when stored at 120 F.

Example 12 This example further illustrates the second coating of the ester-treated alkali hydroxides. To the diethyl phthalate-treated sodium hydroxide of Example powdered boron acetate was admixed in a concentration of 1 percent. .After standing 24 hours at 120 F. the final product was packed in the following formula:

Grams Elon 2.5 Hydroquinone 5.0 Sodium sulfite 25.0 Sodium borate.5H O 25.6

Diethyl phthalate treated sodium hydroxide which has been treated with boron acetate 7.1 Potassium bromide 1.8 Boric anhydride 0.7

The powder did not discolor or otherwise deteriorate when stored at 120 F. However, a sample containing the ester-treated caustic having no second treatment discolored slightly under the same conditions of storage.

Example 13 Grams Elon 2.5 Hydroquinone 5.0 Sodium sulfite 25.0 Sodium borate.5H O 25.6

Diethyl phthalate treated sodium hydroxide which has been treated with the dimethyl terephthalate 7.1 Potassium bromide 1.8 Boric anhydride 0.7

The above powder did not discolor or otherwise deteriorate when stored at 120 F. A similar powder containing only the diethyl phthalate treated sodium hydroxide showed some discoloration when stored under the same conditions.

The second coating over the first treated alkali hydroxide may also be applied by employing the protective materials and methods disclosed in U. S. Patent 2,639,221 of May 19, 1953, to R. W. Henn. The preferred compound disclosed in that patent is phthalic anhydride. However, maleic anhydride, benzoic anhydride, and other compounds mentioned in U. S. Patent 2,384,592 of September 11, 1945, to F. R. Bean may also be employed. Also compounds from the group of substituted phthalic 6 anhydrides such as chlorophthalic anhydride and the group of compounds formedby' the"reaction of boric anhydride with organic anhydrides, such as boroacetic anhydride (or boron acetate) and borophthalic anhydride have been found advantageous for using as the second coat materials. Also 2,2,1-bicyclo-5-heptene-2,3-dicarboxylic anhydride may be so employed.

To apply the second coating, a finely powdered amount of the selected compound is thoroughly mixed with the alkali product formed by the ester treatment method. After mixing the product is allowed to stand in a closed container for a short' period of time preferably at slightly elevated temperatures of up to 120 F. The compound is added to the ester-treated sodium hydroxide in a concentration of 1% by. weight though higher or lower concentrations may also produce equally good results depending on the quality of the original ester-treated alkali hydroxide. I

The second coating treatment can also involve repeating the alkaline hydrolysis ester treatment using, however, a different ester having a very fast reaction rate. Dimethyl-terephthalate, for instance, is not very suitable for use with untreated alkali since the hydrolysis proceeds at such a rapid rate that a good coating is not obtained. On the contrary if this ester is mixed in a concentration of about 1% with a sample of alkali already treated with another ester, which gives only partial stability to the alkali hydroxide at raised temperatures, it will improve the stability of the product'by-reacting with any residual surface alkali.

A further refinementof the multiple treatment process involves dividing the total amount of ester. to be used for the reaction into two or more parts and reacting each part separately in succession, adding each part only after the former has reacted completely. The primary advantage of this method is that it insures complete coating of all the particles of alkali, and results in a more uniform product.

The various treatments also have the advantage of making it easier to prepare the ester-treated caustic in that it is unnecessary :to take as many precautions to drive off the reaction products of the ester treatment completely. As a result it is possible, in some cases to dispense with the evacuation or air stream method of driving' off the alcohol reaction product.

Example 1 granular sodium hydroxide was reacted with a total of 4 cc. of dimethyl phthalate.

However, the ester was divided in four 1 cc. portions and reacted separately. The first portion was thoroughly mixed with the sodium hydroxide and reacted by heating to C. When the reaction was complete, the second portion of ester was added and so on for all four portions. The resulting product was packed in the following single powder de veloper formula:

Grams Elon 2.5 Hydroquinone 5.0 Sodium sulfite 25.0 Sodium borate.5H O 25.6 Dimethyl phthalate treated sodium hydroxide 7.1 Potassium bromide 1.8 Boric anhydride 0.7

Example To give sodium'hydroxidev a protective coating, the following method was used: 50 grams of granular sodium hydroxide was thoroughly mixed withv 1 cc. of diethyl phthalate and the mixture allowedto stand 24 hours at 50 C. This resulted in a product that was dry and free-flowing. 5 grams .of the..treated sodium hydroxide was placed in an uricoveredSO cc. beaker and exposed to room atmosphere conditions for 8 hours after which the product was still uncaked and free-flowing. A sample of untreated sodium. hydroxide exposed under the same conditions became very damp and severely caked.

Example 16 Coating sodium hydroxide with a protective coating by using less reactive esters is demonstrated by the following method: 50 grams of granular sodium hydroxide was mixed in a solution of 8- grams of methyl abietate in 60 cc. of xylene and the mixture heated to gentle reflux for 1 hour. The mixture was then cooled and the solution drained oii. The product was washed with ligroin to free it of unreacted ester and dried giving pale yellow granules. When this treated sodium hydroxide was exposed to room atmosphereconditions it remained uncaked and free-flowing after several hours. Untreated caustic exposed under the same conditionslbecame damp and began to cake after a'few minutes."

The alkali hydroxide to be treated is preferably in granular form. An esterwhich is a liquid atroom temperatures and which will form an easily volatile alcohol is advantageously employed. Solvents may also be employed-to dissolve esters which are solids at room temperature so that coating over all surfaces of the granules will be assured. One may also 'dip the alkali in the undiluted ester, or a solution of the ester, and then allow the sample to drain while the reaction takes place. The ester may be dissolved in an inert solvent such as benzene, toluene or xylene to control thereaction rate or to make it possible to heat the reaction mixture.

By the proper selection of ester itis possible to choose among a wide variety of acids to form the salt coating. It is also possible to select the alcohol to be liberated according to the needs of the process. Ester hydrolysis is accomplished without production of water, as occurs when an acid or anhydride is neutralized. Instead the alcohol combined in the ester is liberated and removal of this alcohol is a much simpler matter than removal of water from a caustic alkali. Furthermore the reaction is allowed to complete itself so that the coating does not 8 continue to react with the sodium hydroxide on standing and thus produce a reactive surface.

I claim:

1. A stable single powder photographic developer composition which resists deterioration when heated to F. containing an organic silver halide developer, a basic ingredient selected from the group consisting of alkali borates and sulfites and an alkali hydroxide in the form of finely divided particles selected from the group consisting of sodium, potassium, and lithium hydroxide having a first protective coating thereover of sodium phthalate and a second protective coating on said first protective coating selected, from the group consisting of sodium chloro phthalate, boron acetate, and 2,2,l-bicyclo-5- heptane-2,3-dicarboxylic anhydride.

2. A stable single powder photographic developer composition which resists deterioration when heated to 120? F. containing an organic silver halide developer, a basic ingredient selected from the group consisting of alkali borates and sulfites and sodium hydroxide in the form of finely divided particles having a first protective coating thereover of sodium phthalate and a second protective coating thereover of sodium chloro phthalate.

3. A stable single powder photographic developer composition which resists deterioration when heated to 120 F. containing an organic silver halide developer, a basic ingredient selected from the group consisting of alkali borates and sulfites and sodium hydroxide in the form of finely divided particles having a first protective coating thereover of sodium phthalate and a second protective coating thereover of boron acetate.

4. A stable single powder photographic developer composition which resists deterioration when heated to 120 F. containing an organic silver halide developer, a basic ingredient selected from the group consisting of alkali borates and sulfites and sodium hydroxide in the form of finely divided particles having a first protective coating thereover of sodium phthalate and a second protective coating thereover of 2,21-bicyclo-5-heptene-2,3-dicarboxylic anhydride.

References Cited in the file of this patent V I UNITED STATES PATENTS 2,266,004

' OTHER REFERENCES Hackhs Chemical Dictionary, Grant 3rd edition, 1954, page 315. 

1. A STABLE SINGLE POWDER PHOTOGRAPHIC DEVELOPER COMPOSITION WHICH RESISTS DETERIORATION WHEN HEATED TO 120* F. CONTAINING AN ORGANIC SILVER HALIDE DEVELOPER, A BASIC INGREDIENT SELECTED FROM THE GROUP CONSISTING OF ALKALI BORATES AND SULFITES AND AN ALKALI HYDROXIDE IN THE FORM OF FINELY DIVIDED PARTICLES SELECTED FROM THE GROUP CONSISTING OF SODIUM, POTASSIUM, AND LITHIUM HYDROXIDE HAVING A FIRST PROTECTIVE COATING THEREOVER OF SODIUM PHTHALATE AND A SECOND PROTECTIVE COATING ON SAID FIRST PROTECTIVE COATING SELECTED FROM THE GROUP CONSISTING OF SODIUM CHLORO PHTHALATE,BORON ACETATE, AND 2,2,1-BICYCLO-5HEPTANE-2,3-DICARBOXYLIC ANHYDRIDE. 